The Collaborative International Dictionary of English v.0.48:

Preserver \Pre*serv"er\, n.
   1. One who, or that which, preserves, saves, or defends, from
      destruction, injury, or decay; esp., one who saves the
      life or character of another. --Shak.
      [1913 Webster]

   2. One who makes preserves of fruit.
      [1913 Webster]

   Game preserver. See under Game.
      [1913 Webster]

WordNet (r) 3.0 (2006):

preserver
    n 1: a skilled worker who is employed to restore or refinish
         buildings or antique furniture [syn: refinisher,
         renovator, restorer, preserver]
    2: a cook who preserves fruits or meat
    3: someone who keeps safe from harm or danger
    4: rescue equipment consisting of a buoyant belt or jacket to
       keep a person from drowning [syn: life preserver,
       preserver, flotation device]